CN101636973B - Method and device for dividing header stack of business unit - Google Patents

Abstract

A method of partitioning a header stack of a data packet, the header stack conforming to a label switching protocol and comprising a plurality of headers, each of the headers comprising a label field to which a label value can be assigned, such that a label switching node can Routing said packet in a network routing domain of a label switching protocol in a communication system comprising a plurality of networks, the method comprising the steps of: receiving said packet at an edge node of a routing domain in said communication system; and The label header stack is processed at the edge node to add a new stack entry with a label field containing a link to the header stack between one stack domain and at least one other stack domain The value delimited by an entry, said one stack domain may be set by said node belonging to the first operational domain of said label switching protocol of said communication system, and said at least one other stack domain may be set by said node belonging to said communication system The node of another routing domain of the system is set, thus the MPLS transmission network solution can be realized.

Description

Method and device for dividing header stack of business unit

technical field

The present invention relates to a method of partitioning a Multiprotocol Label Switching (MPLS) header stack into different domains, and in particular but not exclusively to a method of sending over one instance of an MPLS transport network protocol conforming to another instance of the MPLS transport network protocol. The method of service of the instance (referred to in the art as "MPLS over MPLS"). the

Background technique

MPLS was originally conceived as a method for improving the packet forwarding performance of Internet Protocol (IP) routers. However, MPLS was then extended to carry other layer network technologies (eg, Asynchronous Transfer Mode (ATM), Frame Relay (FR), Plesiochronous Digital Hierarchy (PDH), etc.) using Pseudowire (PW) encapsulation technology. The architecture of the MPLS standard is described in RFC 3031 titled "Multiprotocol Label Switching Architecture" submitted to the Internet Engineering Task Force (IETF) by E. Rosen et al. in January 2001, and its content is incorporated herein by reference. An electronic copy of this document can be downloaded from URL: www.ietf.org/rfc/rfc3031.txt. the

As is known in the art, MPLS essentially enables faster routing decisions by prepending "labels" that determine the path between one router and the next. These "labels" are essentially labels carried in short packet header fields, which are extracted by switching/forwarding network nodes called Label Switching Routers (LSRs). The LSR is preset to associate a specific label with a specific outgoing port(s), so that traffic containing that label can be routed without having to examine the packet header in detail. This avoids hop-by-hop routing decisions on IP layer network addresses, but instead sends traffic along a path predetermined by a specific set of labels. the

MPLS label stacking is known in the art as a means for implementing MPLS tunneling. To implement MPLS tunneling, bulk transport Label Switched Paths (LSPs) (which act as tunnels) are typically established between multiple provider edge devices in the provider's network using external transport labels, and in each bulk LSP , using internal transport labels to identify individual traffic flows. Each packet may carry many tagged headers organized as a last-in-first-out stack. In normal forwarding through an MPLS network, the LSR only processes the top label (ie, the outermost label). At any LSR, a labeled header may be added to the stack (by a "push" operation performed by the LSR) or removed from the stack (by a "pop" operation performed by the LSR). Label stacking enables the aggregation of multiple LSPs into a single LSP for a subset of routes, which creates a "tunnel". the

Figure 1A shows the MPLS header. The MPLS header is 32 bits in length and includes several function fields. The MPLS stack includes multiple MPLS headers, and Figure 1B shows the position of the MPLS label stack within a frame (or equivalently within a packet). the

As shown in Figure 1A, a conventional MPLS 32-bit header includes a 20-bit label field, a 3-bit EXP (experiment) field, a 1-bit S (stack) field, and an 8-bit TTL field. Here, the TTL field indicates the time to live of the MPLS packet. The S field is the bottom of the stack field, which indicates the position of the MPLS header in the MPLS stack, and S=1 indicates that the MPLS header is at the bottom of the MPLS stack (that is, the innermost position closest to the payload), if the MPLS header is not in the MPLS The bottom position of the stack is then S=0. Figure IB shows how the MPLS label stack entry is positioned above the layer header of layer 2 (eg, data link layer) and below the network layer or layer 3 (eg, IP) header. Other headers may be added, for example, if the payload data is not IP, there may also be a PW Control Word header here. the

Figure 1C shows more clearly for the MPLS stack how the LSR receives the top of the label stack first after the layer 2 (e.g., data link layer) header, while the bottom of the label stack comes last and is closest to layer 3 (e.g., network layer) header. The S bit of the bottom header is set to one. The S bits of all other headers are set to zero. the

Figure 2 shows an expanded diagram of an MPLS stack including three MPLS headers. The upper part of Fig. 2 shows how the three layers of the labeled header of MPLS are stacked within the packet header. The lower part of Fig. 2 shows how the Layer 2 header is followed by two MPLS headers with S=0 and a third MPLS header with S=1 that appears at the bottom of the MPLS stack. the

The theoretical number of MPLS label values that can be provided by the 20-bit label value field of the MPLS header is ²²⁰ . But in practice, some label values are reserved and have special meanings. For further information, please refer to RFC 3032 entitled "MPLS Label Stack Encoding" submitted to the Internet Engineering Task Force Standards Organization ("IETF") by E. Rosen et al. in January 2001 , which indicates that values 0 to 15 are reserved. The content of this document is incorporated by reference into this specification.

When an LSR receives a labeled packet, it first processes the label value at the top of the label stack (ie, closest to the layer 2 header) to look for forwarding information. This enables the receiving LSR to know to which port the packet can be forwarded and/or to know the arbitrary operation(s) to be performed on the MPLS stack before forwarding. Examples of operations performed by the LSR on the MPLS stack include replacing the top label stack entry with another value, and/or popping an entry from the label stack, and/or replacing the top label stack entry, and/or causing one or more Additional entries are pushed onto the label stack. Other operations that an LSR can perform include learning about outbound data link encapsulation and any other information needed to properly forward packets. the

Depending on the values assigned to the MPLS Label field and other fields in the MPLS header stack, the receiving LSR may interpret the Label field in a variety of ways. The label field can be used, for example, as a forwarding label, a source label, or as a function label indicating the operation that the LSR has to perform. the

When used as a forwarding label, the Label Value field of the MPLS header is used as a proxy identifier for the "address" of the destination end point of the LSP. In case this MPLS header is at the top of the LSP MPLS header stack, S=0, however, if it is the only MPLS header in the stack, then S=1. It is used to forward the MPLS service unit in the data plane to the destination based on the hop-by-hop method (except for the case of using PHP (penultimate-hop-popping, the penultimate jump out of the stack), in PHP, the last hop completely moves except forwarding header). the

When used as a source label, the 20-bit Label Value field is used as a Proxy Identifier for the "address" of the LSP's source end point. This functional use of the tagged header means that it is invariably the last entry of the MPLS header stack, so the S bit will be set to one. the

When used as a function label, the label value field identifies a specific action to be taken when received at the LSR. As is known in the art, the reserved value of the label field of the MPLS header specifies a specific function to be performed by the LSR on the received packet. For example, label 14 indicates a router OAM alert that transfers the content of the business unit to the control/management plane for further action. In such tagged headers, the S bit is usually set to 1 (however, this is not always the case for other functional uses). the

S.Bryant proposed the network architecture for transmitting the client MPLS network through the server MPLS network, and submitted it to the Internet Engineering Task Force on October 13, 2006 in the Internet proposal titled "Application of PWE3 to MPLS Transport Networks" explained. A copy of this document is available at https://tools.ietf.orq/id/draft-bryant-pwe3-mpls-transport-00.txt. FIG. 3A shows a current solution to the problem of how to transport traffic from another operator's MPLS network (MPLS network "A") over one operator's MPLS network (MPLS network "B") posed by S. Bryant et al. There are technical solutions. This prior art solution consists in forming MPLS tunneling. In FIG. 3A, an MPLS label switched path (LSP) is created between customer edge nodes CE1 and CE2 located in the domain of the MPLS network "A". The LSP is carried over Ethernet. Set up Ethernet between CE1 and PE2, and set up an Ethernet pseudowire (PW) between provider edge equipment PE1 and PE2 to carry Ethernet services from PE1 to PE2, and set up between PE2 and CE2 Ethernet. Ethernet PW is carried over IP or MPLS PSN. If MPLS is used, then PHP is not used to configure the tunnel LSP. the

The Ethernet transmission PW shown in FIG. 3A can support multiple service LSP instances, for example, a service LSP and a trunk (Trunk) LSP (which can bear aggregation of service instances). The identification of each business instance within the instance aggregate is based on the label, and the service instance can be aggregated to the backbone by pushing the label into the stack, and de-aggregated by popping the label (herein, according to the meaning known in the art use the terms "push" and "pop"). the

The prior art solution proposed by S. Bryant separates two MPLS header stacks by inserting an Ethernet header between the two stacks, as schematically shown in FIG. 3B . It is therefore known in the prior art to functionally separate two MPLS layer networks using an inserted Ethernet layer network header, i.e. to provide a network stack in which MPLS is layered above Ethernet and Ethernet In turn, it is layered above MPLS. This prior art solution separates the two MPLS stacks and enables a complete functional disconnection of the two MPLS networks, e.g. operator A's data/control/management plane from operator B's data/control/management plane isolate. However, this prior art solution has certain limitations, for example, both networks must support the same caching technology (i.e., the server MPLS network and the client MPLS network must support the same Insert Ethernet technology), and this must Between CE devices in an end-to-end manner. This is because the PE device would expect an Ethernet presence, which would be the client PW carried over the intermediary server PSN network. Another limitation is that partitioning is achieved by inserting layer 2 technologies (such as Ethernet) into the MPLS stack, which incurs additional operational overhead, eg, management of degenerated (ie, 1-hop) Ethernet layer networks. the

Therefore, it is known in the prior art that the Ethernet layer is extended end-to-end along the LSP between customer edge (CE1 and CE2) devices. the

Furthermore, it is known in the art to support label switched paths over non-MPLS networks. In European Patent Application EP1 134938 in the name of Nortel Networks Corporation, Barry Hass describes systems, devices and methods for supporting label-switched paths over non-MPLS networks. The system requires that label stack information for packets sent on the LSP be preserved by creating an IP tunnel connecting the first MPLS domain of the LSP with the second MPLS domain on the LSP's non-MPLS domain. The packet and label stack information are encapsulated and sent through the IP tunnel, and the MPLS identifier is included in the header of the encapsulated packet, so that the packet and label stack information can be identified in the second MPLS domain. the

The MPLS transmission network scheme of the present invention is to eliminate the limitation of using MPLS as the transmission network aspect in the existing method, and the existing method requires that the LSP between two client MPLS devices on the MPLS network of the transmission provider be consistent. technology. The present invention is to provide a method of using MPLS as a transport network comprising the steps of: using the infrastructure of a second (server) MPLS network to link two label switching routers located in a first (client) MPLS network (LSR) for interconnection, ie to implement an MPLS client/server relationship over MPLS, which does not require the insertion of different and fixed types of technology in the MPLS header stack to achieve a functional separation of the two MPLS networks. the

Contents of the invention

A first aspect of the invention comprises a method of partitioning a header stack of a data packet, the header stack conforming to a label switching protocol and comprising a plurality of headers, each of these headers comprising a label field to which a label value can be assigned , so that a label switching node can route the packet in a network routing domain of the label switching protocol in a communication system comprising a plurality of networks, the method comprising the steps of: in the routing domain of the communication system receiving the packet at an edge node at the edge node; and processing the label header stack at the edge node to add a new stack entry having a label field labeled with a field for mapping between a stack domain and at least one the value delimited by said header stack entry between other stack domains, said one stack domain may be set by said node belonging to the first operational domain of said label switching protocol of said communication system, said at least A further stack domain may be set by a node belonging to another routing domain of the communication system. the

Thus, label stacks can be delimited by marking out operational boundaries such that one or more nodes located at the edge of or within the operational domain of the communication system can only be bound up to the boundary marker (or within a pair of Boundary markers) to operate on part of the stack. Examples of operational domains include routing domains. the

In one embodiment, the method enables implementation of a Multiprotocol Label Switching (MPLS) transport network scheme in accordance with the present invention. the

In one embodiment, the steps of receiving said traffic unit and processing said header to add stack entries with delimited values are repeated more than once to divide said header stack into a plurality of additional stack domains. the

In one embodiment, each additional stack domain is demarcated by stack entries with different delimiting values. the

In one embodiment, each additional stack domain is divided by stack entries with the same delimit value. the

In one embodiment, the value assigned to said label field of a header and delimiting said header stack entry comprises a reserved value according to a label switching protocol. the

In one embodiment, said stack entry with a delimited value indicates that said header stack is to be divided at a point such that other nodes in the same routing domain as said edge node can only add to Operated by one more additional header in the header stack applied by the same routing field that incremented the stack delimit value. the

In one embodiment, the label switching protocol comprises a multiprotocol label switching (MPLS) protocol. the

Another aspect of the present invention is in order to provide a kind of method that Multiprotocol Label Switching (MPLS) header stack is divided into a plurality of stack control domains, and this method comprises the following steps:

receiving MPLS labeled packets at an MPLS node;

The MPLS node adds a network-defining MPLS header to the packet's MPLS label stack, wherein the label field value of the MPLS header is assigned a predetermined value indicating that the MPLS header is to be modified after the point The MPLS stack is partitioned at such a point that the network of the MPLS nodes can only add one more append to the packet after the network delimited MPLS header and before any other network delimited MPLS header MPLS header to operate. the

Another aspect of the present invention is to provide a method of routing Multi-Protocol Label Switching (MPLS) traffic in a communication system comprising a plurality of MPLS networks comprising a hierarchy of MPLS networks, the hierarchy Each MPLS network in includes a plurality of MPLS nodes, and the MPLS nodes can interface with MPLS nodes at different levels in the hierarchy, so that at each layer of the MPLS network hierarchy, the client MPLS network Able to use another MPLS network in the hierarchy as a server network to route traffic from a first MPLS node in the client MPLS network to another MPLS node in the client MPLS network, the method comprising steps:

an ingress MPLS edge node of the server network receives MPLS traffic from the first MPLS node of the client MPLS network, the MPLS traffic comprising a plurality of packets; and

The ingress MPLS edge node of the server network processes each received packet for a stack entry operable by a node in the client network and a stack entry operable by a node in the server network The MPLS stack for each of the plurality of packets is divided. the

In this way, one MPLS network is transparently transported over another MPLS network by inserting specially reserved labels into the header stack. In one embodiment of the invention, the hierarchy of the MPLS network includes a client/server network hierarchy. the

In one embodiment, said routing of MPLS traffic includes performing switching operations on MPLS traffic by MPLS nodes. the

In one embodiment, the routing of the MPLS traffic includes performing a forwarding operation on the MPLS traffic by the MPLS node. the

In one embodiment, the routing of the MPLS traffic includes performing a routing operation on the MPLS traffic by the MPLS node. the

In one embodiment, said client MPLS network is capable of using another said MPLS network in said hierarchy as a server network in which traffic is transparently routed from said first MPLS node to a second Two MPLS nodes. the

In one embodiment, the above-mentioned method further comprises the following steps:

The egress MPLS edge node of the server MPLS network receives the MPLS service from the ingress MPLS edge node;

the egress MPLS edge node processes each received packet to remove partitions added by the ingress MPLS edge node; and

The egress MPLS edge node performs a routing operation to forward the received MPLS service to the ingress MPLS edge node of the client MPLS network. the

In one embodiment, the method is performed in a communication system comprising a plurality of MPLS networks, wherein a first MPLS node in a first MPLS network of the plurality of MPLS networks is connectable to another one of the plurality of MPLS networks an ingress MPLS edge node in an MPLS network, wherein the ingress MPLS edge node of the other network is connectable to an egress MPLS edge node of the other MPLS network, and wherein the egress MPLS edge node of the other MPLS network is able to Connected to the second MPLS node in the first MPLS network, the method for routing services includes the following steps:

routing traffic from said first MPLS node to a second MPLS node in said first MPLS network using another MPLS network as a transport network;

The ingress MPLS edge node of the second network receives MPLS traffic from the first MPLS node of the first MPLS network, the MPLS traffic comprising a plurality of packets; and

The ingress MPLS edge node processes each received packet for the stack entry operable by a node in the first network and a stack entry operable by a node in the second network. Each MPLS stack is divided into multiple packets. the

In one embodiment, the step of processing each received packet to partition said MPLS stack includes performing the following steps by an ingress MPLS edge node:

adding the network delimiter including the MPLS header with the stack partition value assigned to the label field, the network delimiter added as a stack entry to the MPLS stack of the received packet;

Additional MPLS headers are added to the MPLS label stack after the network delimiter stack entry to forward the received packet to the egress MPLS edge node over another MPLS network. the

Another aspect of the present invention is to provide a communication system comprising a plurality of MPLS networks, the plurality of MPLS networks comprising:

The hierarchy of the client MPLS network and the server MPLS network, each MPLS network in the hierarchy includes a plurality of nodes capable of interfacing with nodes of different levels in the client and server hierarchy, so that the MPLS network client and server In a layer of the hierarchy, the client MPLS network is capable of routing traffic from a first node to a second node in the client MPLS network using another MPLS network in the hierarchy as a server network;

An ingress server MPLS node, which is configured to receive MPLS services from the first MPLS node of the client MPLS network, the MPLS services include a plurality of packets, and the ingress MPLS nodes include:

processor means arranged to process each received packet to map the stack entry operable by a node in the client network to a stack entry operable by a node in the server network The MPLS stack is divided for each of multiple packets. the

In one embodiment, a first MPLS node in a first MPLS network of the plurality of MPLS networks is connectable to an ingress MPLS node in another MPLS network of the plurality of MPLS networks, wherein the other network The ingress MPLS node of said other MPLS network is connectable to the egress MPLS node of said another MPLS network, and wherein said another MPLS network's egress MPLS node is connectable to said second MPLS node in said first MPLS network,

A method of switching/forwarding traffic from a first node to a second node in the first MPLS network using said another MPLS network as a transport network, the method comprising the steps of:

the ingress MPLS node of the second network receives MPLS traffic from the first MPLS node of the first MPLS network, the MPLS traffic comprising a plurality of packets; and

The ingress MPLS node processes each received packet for each of the plurality of packets between a stack entry operable by a node in the first network and a stack entry operable by a node in the second network One of the MPLS stacks is divided. the

Another aspect of the present invention is to provide a method of de-partitioning a header stack of a data packet, said header stack conforming to a label switching protocol and comprising a plurality of headers, each comprising a label field to which a label value can be assigned , so that the label switching node can route the packet in the network routing domain of the communication system, the communication system includes a plurality of networks, the method includes the following steps:

receiving the packet at an edge node of a routing domain of the communication system;

processing a label header stack at said edge node to remove stack entries having a label field comprising a value delimiting a header stack entry between one stack domain and at least one other stack domain, Said one stack domain may be set by a node belonging to a first routing domain of said label switching protocol of said communication system, and said at least one other stack domain may be set by a node belonging to another routing domain of said communication system. the

Partitions are removed from the header stack by removing partitions in the header stack. Parts of the label stack are returned to their disjoint form. In this way, the two tag stacks are physically or logically separated after de-partitioning (ie after removing the boundary markers in the stacks). For example, the two label stacks are physically/spatially disjoint when in their parent MPLS network, and/or logically disjoint when one stack is hosted on the other. the

In any given data packet, a number of headers are appended according to one or more protocols (eg, see Figure 2), eg layer 2 and/or layer 3 headers may be present. An example of a header stack conforming to a label switching protocol is a multiprotocol label switching header stack. the

The label field, to which a label value can be assigned, enables a label switching node to perform certain operations on packets in the routing domain of the network, eg, routing, forwarding, and the like. In some embodiments of the invention, not all labels have routing (eg, destination address (DA) proxy forwarding) semantics. Some tags have source semantics, some tags have native action semantics, and so on. Thus, the label field enables label switching nodes to take appropriate actions for the assumed label semantics. the

Another aspect of the present invention is to provide a label switching node arranged to implement a method of partitioning a header stack of a data packet, said header stack conforming to a label switching protocol and comprising a plurality of headers, each of which comprising a label field to which a label value can be assigned to enable a node to route said packet in a network routing domain of said label switching protocol in a communication system comprising a plurality of networks, the method comprising the steps of :

receiving said packet at said node;

The label header stack is processed at said node to add a stack entry having a label field comprising a field delimiting said header stack entry between a stack field and at least one other stack field value, the one stack domain may be set by a node belonging to a first routing domain of the label switching protocol of the communication system, and the at least one other stack domain may be set by a node belonging to another routing domain of the communication system. the

Another aspect of the present invention is to provide a communication signal comprising a plurality of data packets, each packet comprising a header and a payload, the header comprising a header stack comprising a plurality of header fields all conforming to the same label switching protocol , wherein at least one header field is assigned a value indicating that after said header, all domains different from the operating domain of a node conforming to said label switching protocol that previously operated on said header field's stack entry can be assigned A node in the operational domain of the label switching protocol operates on a stack entry conforming to the header of the label switching protocol. the

The operational domain may include a routing domain, or a forwarding domain, or any other suitable domain where a node may perform actions. the

Another aspect of the present invention is to provide a communication signal comprising a plurality of data packets, each packet comprising a header field and a payload, the header field comprising a header stack having a plurality of header fields, combined with the plurality of header fields The label assignment protocol of another header field in the field is different from the label assignment protocol to increase at least one header field in the plurality of header fields, wherein at least one header field is assigned the following value, which value is indicated in the header A node conforming to the label switching protocol may then be routed by a node in a routing domain of the label switching protocol that is different from the routing domain of a node conforming to the label switching protocol that previously operated on a stack entry of the header field The header's stack entries are manipulated. the

In some embodiments of the invention, the label field values in the header stack are incremented by different types of label allocation protocols. the

The MPLS header fields may be provided by networks associated with different control domains. In some embodiments of the invention, the stack of MPLS headers all belong to the same network party. the

Another aspect of the present invention is to provide a communication system comprising a plurality of multi-protocol label switching communication networks, each said communication network comprising a plurality of network nodes configured to implement a multi-protocol label switching domain of operation, the communication system comprising : A border node located between the two communication networks, the border node includes: a receiver, which is configured to receive an MPLS service unit; and one or more processors, which are configured to receive The MPLS header stack of the incoming service unit is processed to include the delimited label field value indicating the operational boundary of the MPLS operational domains of the two communication networks. the

In one embodiment, said node is an ingress node to one of said two communication networks, and wherein said node further comprises one or more processors, said one or more processing The implementer is arranged to perform the processing of processing said header stack to contain one or more other MPLS header field values after assigning said Operational Boundary Label field value such that the communication network at said ingress node Other nodes in the operation domain of can perform one or more operations on the business unit. the

In one embodiment, said delimited tag field value is processed by another node in said communication network and is not assigned to said delimited tag field value by a node located in the operating domain of the other of said two communication networks. operates on the tag field value of the header stack described above. the

In one embodiment, the node receiving the traffic unit in the communication network only processes the header stack up to the value of the delimited tag field, and ignores the A node in the operational domain of the communications network assigns to an arbitrary label field value of the header stack. the

In one embodiment, the type of the multi-protocol label switching protocol differs between at least two communication networks of the plurality of communication networks. the

According to the division scheme of the present invention, the IP address in the client MPLS layer network is regarded as irrelevant, and the client IP address does not need to be known in the server layer MPLS network. In contrast, the present invention transparently hosts a client layer MPLS network over a server layer MPLS network. the

Various aspects of the present invention have been set forth above and are given by the appended independent claims, preferred embodiments and dependent claims. It will be apparent to those of ordinary skill in the art that the various aspects and preferred embodiments may be combined in any suitable manner. the

Description of drawings

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, which are examples only, in which:

Figures 1A to 1C show various diagrams of conventional MPLS headers;

Figure 2 shows an expanded diagram of how the MPLS fields are set in a stack in the MPLS header;

Fig. 3 A shows the MPLS transmission network scheme of prior art;

Figure 3B shows how the intermediate technology (Ethernet) separates two separate MPLS transport stacks in the prior art solution shown in Figure 3A;

Fig. 4 A has shown wherein can realize the communication system of MPLS transmission scheme according to an embodiment of the present invention;

Figure 4B shows more details of the MPLS transport network scheme according to an embodiment of the present invention;

Figure 4C shows the divided MPLS stack according to an embodiment of the present invention;

Figure 5A and Figure 5B show the divided MPLS stack according to an embodiment of the present invention, wherein S=0 in the divided MPLS stack entry;

Figure 6A and Figure 6B show the divided MPLS stack according to an alternative embodiment of the present invention, wherein S=1 in the divided MPLS stack entry;

Figure 7A shows a communication system for which a recursive stack MPLS transport scheme according to one embodiment of the present invention is provided; and

Figure 7B shows how to divide the MPLS stack multiple times to implement one embodiment of the present invention for the communication system shown in Figure 7A. the

Detailed ways

The best mode and each preferred embodiment of the present invention currently conceived by the inventors are described below. Those of ordinary skill in the art can understand that it is obvious that a specific component or step contains specific features necessary for the realization of the present invention, even if these features are not explicitly listed (this is for the sake of clarity in the description) for purposes of clarity and brevity, and these features are considered implicitly included unless expressly stated to the contrary). All technical terms described herein retain the meanings assigned to them by RFC 3031 and RFC 3032 (as above), unless otherwise expressly indicated to the contrary. the

The term "traffic unit" means a packet, cell, frame and/or any other suitable component of traffic. The various types of business units are used herein as synecdoches for other types of business units and are considered equivalents for the purposes of the present invention. For consistency with RFCs 3031 and 3032, which use the term MPLS "packet," the term should be used consistently here, however, those of ordinary skill in the art will appreciate that reference to the term "packet" is to be used for any appropriate equivalent. References to business units of price type, unless the context of the word "grouping" clearly indicates otherwise. the

Fig. 4A shows a communication system 1 comprising a plurality of networks 2 and 3 (networks 2 and 3 respectively comprising a plurality of nodes 4a, 4b, 5a, 5b) according to the invention. the

The nodes 4a, 4b, 5a, 5b of each network are configured to implement label switching or forwarding of received service packets, and in one embodiment, these nodes include And realize the Label Switching Router (LSR). the

According to the invention, in each network 2, 3 at least a plurality of nodes 4a, 4b, 5a, 5b are adapted to interface with at least one other node of said plurality of networks. These nodes comprising an outwardly facing interface with another network are referred to herein as edge nodes. Depending on the direction in which the edge node performs label switching/forwarding operations on the service flow, the edge node acts as an ingress node for the service flow entering the specific network or as an egress node for the service flow leaving the specific network. the

Each network 2, 3 may have the same or a different type of control and/or management plane technology as another network in the communication system. But in each network 2, 3, all nodes are located in the same operation (e.g., routing), i.e., in Fig. 4A, nodes 4a and 4b belong to one operation (e.g., routing) Different operational (eg, routing) domains. In one embodiment of the present invention, two or more (or all) of the plurality of networks forming the communication system may have the same administrative domain. In another embodiment of the invention, two or more (or all) of the plurality of networks forming the communication system may have different administrative domains. the

Accordingly, communication system 1 includes two or more different MPLS networks, each MPLS network includes at least one different control-plane instance, and in some embodiments, all functional components (such as control-plane , management plane and data plane) are independent. In one embodiment of the invention, the two or more MPLS networks belong to the same operator (for example, different business lines may belong to the same operator), but, in an alternative embodiment, they belong to different Operators (eg, different network operators). the

As mentioned above, an embodiment of the invention is shown in FIG. 4A , wherein the plurality of networks includes two MPLS networks 2 , 3 denoted MPLS Network A and MPLS Network B . There are two edge nodes A1 and A2 in MPLS network A, and there are two edge nodes B1 and Bn in MPLS network B, and the label switched path (LSP) 6 indicated by the dotted curved arrow reaches A2 from A1 via B1 and Bn . Nodes A1 and A2 are located in the operational (eg, routing) domain of network A, while nodes B1 and Bn are located in the operational (eg, routing) domain of network B. the

defines the term "MPLS node" to be consistent with RFC 3031, which defines an MPLS node as a node capable of running MPLS and aware of the MPLS control protocol, capable of running one or more routing protocols, and capable of label to forward packets. In Fig. 4A, nodes 4a, 4b and 5a, 5b form part of a single MPLS network domain. According to RFC 3031, an MPLS network domain includes a contiguous collection of nodes that perform MPLS operations such as routing and forwarding and are also located in a routing domain. the

For the sake of simplicity, in each of these two MPLS networks 2, 3, only two edge nodes A1 and A2 (for example, LSRs) located in the MPLS network, and only two Edge nodes B1 and Bn (eg, also LSRs). However, those skilled in the art can understand that in any actual deployment, each MPLS network probably includes multiple nodes, and several nodes may provide core node and edge node functions. the

In one embodiment of the invention, the administrative control over network A is different from the administrative control over network B, for example, network A is in the domain controlled by the first network operator "A", while the administrative control over network B Control is in a domain controlled by another network operator "B". However, in alternative embodiments, operator entities "A" and "B" may be the same. the

Consider the case where operator A would find it advantageous to send traffic (MPLS packetized data) along LSP 6 via operator B's MPLS network from node A1 via nodes B1 and Bn to another node A2. This requires packets to enter MPLS network B via ingress edge node B1 and leave MPLS network B at egress edge node Bn. It will be apparent to a person skilled in the art that in practice the LSP 6 between nodes B1 and Bn may traverse multiple nodes in operator B's network. the

Conventionally, when sending MPLS traffic between LSRs in an MPLS network, each LSR queries a routing table (called a Label Information Base (LIB)) including MPLS label information. Each LSR performs a lookup operation on the LIB using the ingress interface and ingress label of the received MPLS packet, which enables the egress interface and egress MPLS label to be determined, the LSR then forwards the received packet via the egress interface indicated by the LIB, Replace inbound labels with outbound labels. Although individual labels are only associated with specific links between adjacent LSRs, collectively the LSR table will create label-switched paths on the MPLS network. An MPLS stack includes multiple MPLS labels, and conventionally only the outermost (last) label is used for forwarding. The outermost MPLS label is "popped" (ie, removed) by indicating the appropriate entry in the LSR label table. This enables removal of one or more MPLS labels at the egress LSR by providing a suitable indication in the LIB at the egress LSR. However, some means are required to prevent the use of Carrier B's MPLS network as a transit network in such a way that Carrier A uses the S bit (and indeed all other functions) independently in these two MPLS networks Stack entries associated with network A are manipulated by LSRs associated with network B. This enables a client/server relationship to be established between a Network A MPLS node acting as a client and a Network B MPLS node acting as a server. As shown in FIG. 4A , this makes MPLS node A1 and MPLS node A2 directly peers, while MPLS nodes B1 and Bn establish server transport capabilities for operator A's services. the

This requires a partitioning mechanism in the MPLS stack such that operator B's edge and core MPLS nodes (B1, B2...Bn) do not have access to MPLS nodes in operator A's client MPLS network (A1, A2) The ability to control the assigned tags. the

This partitioning mechanism of the present invention enables this client/server relationship to be established between these two MPLS networks 2, 3, referring now briefly to FIG. Added to the problems associated in the MPLS stack 11 including those MPLS headers 8a already applied by network A. The stack partition 9 proposed by the present invention is used as a buffer or network delimiter between the two MPLS stack control domains, i.e., the stack partition 9 divides the network stack entries shown in FIG. Each of the two MPLS networks independently sets the S bit in the MPLS stack entry. the

A potential advantage of the present invention is that an MPLS transport network scheme is provided where the present invention differs from conventional practice with regard to the type of section layer technology interconnecting client devices with server devices. While in one embodiment, the same communication technology is used to support communications between client devices and servers at each end of the LSP, in alternative embodiments this need not be the case. the

In Fig. 4B, the drawing is arranged so that the differences from the prior art solution shown in Fig. 3A are more apparent, but the elements of the communication system are labeled to remain the same as those shown in Fig. 4A. Figure 4B of the accompanying drawings shows how, in one embodiment of the present invention, the technology (i.e., the communication protocol) that supports communication between edge nodes A1 and B1 (CE1 and PE1 in Figure 3A) ) is different from the technique used between Bn (provider equipment PE2 in FIG. The technology is different. Thus in FIG. 4B a first communication protocol (corresponding to the first type of segment layer technology shown as layer 2 #1 in FIG. 4B ) is used between A1 and B1, while a different communication protocol is used between Bn and A2. The segment layer communication protocol (shown as layer 2#2 in FIG. 4B ). In each case, there is no intermediate end-to-end layer network technology between B1 and Bn - the MPLS traffic from network A is not separated by any intermediate technology headers from the MPLS traffic from network B. Although referred to as Layer 2 in FIGS. 4A and 4B , "Layer 2 #1" and "Layer 2 #2" do not always denote OSI protocol layers. In some embodiments of the present invention, depending on the specific implementation of the present invention, the segment layer represents any suitable connection-oriented circuit switching (CO-CS), connection-oriented packet switching (CO-PS) or Connectionless Packet Switching (CL-PS). For example, one of ordinary skill in the art may use the term "layer 2" to refer to the CO-PS layer, while the term "layer 3" may be used to refer to the CL-PS layer. the

In the context of some embodiments of the invention, the term "segment layer" denotes the very bottom of the network stack (i.e., the actual or physical layer), where information (binary signals from higher layers) needs to be encoded (dictionary-mapped) as A form suitable for modulation onto electromagnetic waves (which may be guided on solid physical media such as copper or optical fibers, or may include, for example, free-space electromagnetic waves propagating as radio waves). Because MPLS does not have a segment layer specification, MPLS relies on having some other layer network technology below the MPLS layer (even for degraded networks such as point-to-point single-hop networks). In some embodiments of the invention, these lower-layer networks are "real" networks in the sense that they themselves create multi-hop switched connections. the

In FIG. 4C , a single MPLS stack is divided between a stack entry whose label has been assigned a value by a device in network A and a stack entry whose label has been assigned a value by a device in network B. In FIG. The header 11 of the MPLS packet shown comprises a layer 2 header element 7 , a layer 3 header element 10 and an MPLS header stack 12 . In this embodiment, the MPLS header stack 12 includes two MPLS network headers (8a and 8b) and a network delimiter stack entry 9 in different A functional division is provided between the sets of stack entries 8a and 8b of the routing domain. The network delimiter stack entry 9 enables this two-layer MPLS network to implement network hierarchies, for example by working in a client/server mode. the

In this way, the present invention enables a single MPLS stack to carry MPLS headers conforming to different values assigned in individual networks, and enables MPLS networks to remain functionally independent. Here, the terms "layer 2" and "layer 3" may refer to OSI layers, and/or, in some embodiments, "layer 2" simply refers to any suitable connection-oriented packet switching layer technology, while "layer 3" refers to Any suitable connectionless packet switching layer technology. the

The present invention seeks to define a predetermined value that is assigned to the 20-bit MPLS label field and indicates that the MPLS header stack is divided into sub-partitions, either alone or in combination with other MPLS header fields, these The subdivisions respectively contain header values independently assigned by devices located in a specific MPLS network domain. The above-mentioned limitations of the prior art for MPLS transport networks are mitigated and/or eliminated by ensuring that individual MPLS network domains do not attempt to reassign these values as header fields set in another MPLS network domain. Advantageously, by dividing the MPLS header stack into different network domains, the MPLS header stack can be used recursively, so that a multi-depth transport network can be provided hierarchically, as schematically shown in Figure 7A and Figure 7B of the accompanying drawings and as described later. the

The invention includes inserting into the label field of an MPLS stack entry a stack partition value which has the function of separating the MPLS stack into two or more separate stack control domains, each stack control domain being associated with a separate MPLS network Associated. In this way, the stack partition value is used as a network delimiter. Separate stack entries whose values have been assigned by the control or management plane of one network operator from those whose values have been assigned by another network operator by a network delimiter stack entry with a stack demarcation tag value . Thus, a network delimiter according to the invention comprises an MPLS stack entry whose label field has a stack partition value that has been assigned by the server MPLS network domain. the

The network delimiter is inserted by an adaptive function between the client MPLS network and the server MPLS network, which is implemented by the server layer network. Submit MPLS packets from the client MPLS network (referring to Figure 4A, i.e. network A) to the server MPLS network (network B in Figure 4A), and the ingress node B1 at the edge of the MPLS at the server layer forwards two new MPLS The header is attached to the MPLS stack. The first MPLS stack entry contains a network delimiter (the network delimiter includes an MPLS header with a predetermined stack division value), while the second header is a "normal" MPLS header for forwarding through the server layer network. At the egress edge node of server MPLS network B (shown as Bn in FIG. 4A ), these stack entries are removed, and the client MPLS packet is submitted to client MPLS network A. After the egress edge node Bn has popped its final forwarding header, the egress edge node Bn can only "see" the "network delimiter" stack entry. The presented network delimiter label informs the edge node Bn that the next header is an MPLS packet belonging to a different MPLS network. the

Since each node along the LSP does not add a new labeled header during normal forwarding, if node B1 applies "stack delimiter" + "normal forwarding" to these two headers, then between B2 and B3 "Normal forwarding" headers are exchanged between B3 and B4, and so on, until the node Bn receives the packet. This means that along the LSP from B1 to Bn, the stack depth remains 2, while "stack delimiter" header. In some implementations, more headers are added to the packet en-route between B1 and Bn, however, this will create an en-route between the nodes that add the header(s) (e.g., between B1 and Bn Between some arbitrary intermediate nodes Bk and Bm) get lower LSP. The intermediate nodes Bk and Bm respectively add/remove these additional header(s), so that eg they are not present when the packet arrives at Bn. the

The above example is shown in Fig. 5A and Fig. 5B. In Figures 5A and 5B, an example of a two-layer MPLS network header stack is shown. Figures 5A and 5B show the presence of a predetermined "split" value and the S=0 bit in the label field of a stack entry, which indicates that the MPLS header above the network delimiter belongs to a different MPLS header than the MPLS header below the network delimiter. MPLS network. Each of these headers is typically subject to different administrative controls. the

In Fig. 5A, there is only one S=1 stack entry in the MPLS stack, which is consistent with current MPLS standards such as summarized in RFC 3031, RFC 3032, etc., and in the division of network B, for the label stack entry (# B1 and #B2) and set the S bit to 0. Figures 5B, 6A and 6B illustrate alternative embodiments that allow setting of one S=1 bit in each stack control field associated with a particular MPLS network. the

In Figure 5B, in each partition of the MPLS stack, the stack entry closest to the end of the layer 3 header of the MPLS stack is assigned the S=1 bit, and the network delimiter is assigned the intermediate S=0 value. Figures 6A and 6B show an alternative embodiment in which the network delimiter is not represented by the S=0 bit but is associated with the S=1 bit, however, different embodiments of the present invention may have different effects on the network delimiter The S bits assign different values. the

Referring to FIG. 4A again, the MPLS transmission scheme according to an embodiment of the present invention will be described in more detail for the service flow from left to right (as shown by the dotted line with arrows in the figure). For bidirectional traffic, similar functionality can be provided in the opposite direction. In order to implement the transmission scheme according to the invention, operator B establishes (by arbitrary mechanism) a standard MPLS LSP (here called LSP_X) between nodes B1 and Bn. Under normal circumstances LSP_X has a header with a single MPLS label, and forwarding labels are usually (but not always) exchanged at each hop. In addition to containing the forwarding label, encode another MPLS header field as: S = 1, EXP = any value considered to provide sufficient performance for the purpose of MPLS client packets from network A that this LSP_X is ultimately to carry, TTL = any length sufficient to get from B1 to Bn. In one embodiment, PHP is used on LSP_X, however, this is not the best mode of the invention conceived by the inventors. This is to ensure normal MPLS forwarding headers, specifically where the last-hop forwarding label is visible at node Bn. This provides a clear indication of which packets received by Node Bn are associated with LSP_X (rather than any other LSP terminating at Node Bn). the

B1 is arranged in any conventional manner known to those of ordinary skill in the art to expect to receive MPLS packets from operator A's node A1 at some incoming port of node B1. MPLS packets from node A1 can have any allowed label value, S value, EXP value and TTL value. These MPLS packets are transparently carried by the MPLS network of operator B in a hierarchical manner (eg, client/server) by using the MPLS transport scheme of this embodiment of the present invention. The server segment layer connecting nodes A1 and B1 is any suitable communication technology capable of transparently carrying MPLS packets in a hierarchical manner (eg client/server), eg Ethernet known to those of ordinary skill in the art. This "connection" for the communication technology between A1 and B1 is functionally completely terminated at A1 and B1 , ie in particular it does not extend through operator B's MPLS network. the

Another server-level technical "connection" is also established between nodes Bn and A2, and it fulfills the same requirements as the above-mentioned server-level connection between A1 and B1. Although in some embodiments of the invention, the server segment layer technology between A1 and B1 and the server segment layer technology between Bn and A2 are different, in other embodiments, between A1 and B1 and between Bn and A2 The same server segment layer technology is provided between A2. In general, the manner in which the server-level technical connections are established between A1 and B1 and between Bn and A2 has no influence on the configuration of the MPLS transport network solution according to the invention. the

Referring again to Figure 4A in the accompanying drawings, when an MPLS packet arrives at node B1 from node A1, node B1 performs at least the following operations on the MPLS stack of the received packet:

(i) adding an MPLS header including a network delimiter to the MPLS packet from node A1; and

(ii) Add another MPLS header after the Network Delimiter header with the type that B1 would normally assign to forward the packet from B1 to Bn along the LSP_X above. the

The net delimiter added by B1 contains a label field that is assigned a stack partition value. This effectively indicates that this part of the MPLS network stack has terminated and that following the network delimiter is an MPLS stack entry belonging to a different MPLS network. It is up to the ingress node B1 of network B to assign appropriate values to the other fields of the network delimiter stack entry, such as the S bit (e.g., S=0 (recommended), although S=1 could also be used), the EXP field (e.g., EXP = optional) and TTL field (TTL = 1 (recommended)). The value of the TTL field is assigned (TTL = 1 (recommended), although other TTL values may be used) to prevent packets from being forwarded incorrectly if they were mistransmitted. the

Other MPLS headers added to the MPLS stack by B1 are also assigned values in the normal way for the MPLS header in network B, e.g. the S bit is set to S=0 (recommended, although theoretically if this is the case for B1 with At the bottom of the stack of the normal forwarding header in network B between Bn, S=1) can be used, the EXP field value is set to provide sufficient , while the TTL field value is set to an arbitrary value sufficient for the packet to reach Bn from B1. the

MPLS packets from node A1 encapsulated as described above are then transported transparently through operator B's network (in LSP_X) until they reach node Bn. When node Bn removes LSP_X's normal MPLS forwarding header, this exposes the network delimiter stack entry. This indicates that after the network delimiter stack entry there is a further set of one or more MPLS headers belonging to another MPLS network (ie in this case the MPLS network of operator A) in the MPLS stack. Node Bn then removes the network delimiter stack entry and, because of the previous setup, is able to know from which port it can be sent out of node Bn to reach node A2 in operator A's network. the

One embodiment of the invention uses a label signaling protocol (eg, LDP or RSVP-TE) to distribute labels between nodes (eg, from node Bn to node B1) and to set these nodes. All labels (including stack partition labels) can be allocated in this way in the relevant MPLS network. In other embodiments, label assignment and provisioning may be performed by management and/or OSS techniques. These are conventional techniques known to those of ordinary skill in the art. the

Figures 7A and 7B of the accompanying drawings illustrate how the invention can be extended to represent a multi-layered scenario of an MPLS network including a hierarchy of client/server relationships. As shown in Figure 7A, the MPLS service from the network of operator A uses the MPLS network of operator B as the transmission network, and the MPLS network of operator B further uses the MPLS network of operator C as the transmission network, and the MPLS network of operator C Further, the MPLS network of operator D is used as the transport network. Fig. 7B shows the multi-divided MPLS stack, in which multiple stack divisions #1, #2, #3 are shown. This enables the MPLS stack entries of various network operators to be kept concatenated together in the MPLS stack through the data-plane encapsulation technology for MPLS services proposed by the present invention. the

Referring to the two-layer implementation of the present invention, the ingress LSR and Egress LSR, while appending the MPLS stack partition value as a network delimiter stack entry. the

One embodiment of the invention does not enforce a relationship between the stack partition value used in network A and any stack partition value used in network B. In various embodiments of the invention implemented for three or more layers of MPLS transport networks, there is also no requirement for any relationship between any one of the stack partition values used for network delimiters (e.g., as shown in Figure 7 and As shown in FIG. 7B , the MPLS transport network solution of the present invention is used in a recursive stacking manner (for example, MPLS over MPLS (MPLS-over-MPLS-overMPLS), etc.)). the

In one embodiment of the invention, a global reserved value (ie, one of the values in the reserved label set 0-15) is assigned to the stack partition value used by the entire MPLS network. However, the use of global reserved values is not necessary to implement the invention. Any value may be used for the stack partition value as long as the MPLS network that assigns the value to the LSP can ensure that the stack partition value can be understood within the context of the LSP carrying the stack partition value. In the MPLS network, the stack division value may or may not be unique. the

Various modifications and functional equivalents to the various features of the invention described herein will be readily apparent to those skilled in the art and are intended to be implicitly included in the description unless expressly excluded by the description. Such modifications and functionally equivalent features, as well as any features that are essential to the practice of the invention but omitted for clarity and brevity, will be apparent to those of ordinary skill in the art. the

In some embodiments of the invention, the term "technology" may refer to segment-level technology, unless the context of the term indicates otherwise. For example, in one embodiment of the present invention, "communication technology supporting communication between edge nodes" may refer to "segment layer" technology. the

Here, the terms "Multiprotocol Label Switched" or "Multiprotocol Label Switching" and the acronym "MPLS" are used to denote the standard protocol, and implicitly any variant protocol with similar header structure restrictions, e.g., Transport MPLS (TMPLS, TMPLS is supported by the International Telecommunication Union (ITU), more information about TMPLS can be obtained from the website http://www.transport-mpls.com) and so on. Accordingly, the term "MPLS" should be considered to encompass variations and derivatives associated with MPLS protocols such as T-MPLS, wherever appropriate in the above description. the

The terms "traffic unit", "packet", "cell" and "frame" are intended to be used as synonyms for each other, and they are considered equivalent for the purposes of this invention, although the above referenced RFC 3031 and RFC 3032 uses the term "MPLS packet" as used herein for consistency. the

It will be apparent to those of ordinary skill in the art that the use of "layer 2" and "layer 3" herein may refer to OSI layer 2 (data link) and layer 3 (network) technologies, and/or to refer to connectionless packet switching And connection-oriented packet switching (or connection-oriented circuit switching) communication protocol. the

The summary text is repeated here to form part of the specification:

A method of partitioning a header stack of a data packet, the header stack conforming to a label switching protocol and comprising a plurality of headers, each of the headers comprising a label field to which a label value can be assigned, such that a label switching node can Routing said packet in a network routing domain of a label switching protocol in a communication system comprising a plurality of networks, the method comprising the steps of: receiving said packet at an edge node of a routing domain in said communication system; and The label header stack is processed at the edge node to add a new stack entry with a label field containing a link to the header stack between one stack domain and at least one other stack domain The value delimited by an entry, said one stack domain may be set by said node belonging to the first operational domain of said label switching protocol of said communication system, and said at least one other stack domain may be set by said node belonging to said communication system The node of another routing domain of the system is set, thus the MPLS transmission network solution can be realized. the

Claims (14)

1. A method of dividing a header stack of a business unit, said header stack conforming to a label switching protocol and comprising a plurality of headers, each of these headers comprising a label field capable of assigning a label value to it, so that label switching The node is capable of operating the service unit in a corresponding operation domain of a label switching protocol communication network in a communication system including a plurality of label switching protocol communication networks, the method comprising the following steps: receiving said traffic unit at an edge node of a first operational domain of said label switching protocol communication network in said communication system; Processing a label header stack at said edge node to add a new stack entry having a label field comprising a boundary for said header stack entry between one stack domain and at least one other stack domain The value of a flag, said one stack domain can be set by a node belonging to said first operational domain of one said label switching protocol communication network of said communication system, and said at least one other stack domain can be set by a node belonging to said communication system It is set by a node of another operation domain of another label switching protocol communication network. 2. The method of claim 1, wherein the label switching protocol comprises a multi-protocol label switching protocol. 3. The method of claim 1, wherein the label switching protocol comprises Transport Multiprotocol Label Switching Protocol. 4. A method according to any one of claims 1 to 3, wherein said traffic units comprise data packets. 5. The method according to any one of claims 1 to 3, wherein the operational domain comprises a routing domain, and wherein the label value can be assigned to enable a label switching node to pass through various nodes in the communication network The service unit is routed in the routing domain to operate on the service unit. 6. The method according to any one of claims 1 to 3, comprising the steps of repeating the steps of receiving said traffic unit and processing said header to increase a stack entry with a delimited value for more than Once, to mark the boundaries of the header stack entries, thereby dividing the header stack into a plurality of additional stack domains. 7. The method of claim 6, wherein each additional stack domain is demarcated by stack entries having different delimiting values. 8. The method of claim 6, wherein each additional stack domain is divided by stack entries having the same delimit value. 9. A method according to any one of claims 1 to 3, wherein said value assigned to said label field of a header and delimiting said header stack entry comprises a reserved value according to a label switching protocol . 10. The method according to any one of claims 1 to 3, wherein said stack entry having a delimit value indicates that said header stack is to be divided at a point such that the edge node Other nodes located in the same routing domain can only operate on one more additional header added to the stack of headers applied by the same routing domain increasing the stack delimit value. 11. An apparatus arranged to partition a header stack of a traffic unit in a communication network, said header stack conforming to a label switching protocol and comprising a plurality of headers, each of these headers comprising a A label field, so that a label switching node can operate the service unit in a network operation domain of the label switching protocol in a communication system including a plurality of networks, the device comprising: a receiver arranged to receive said traffic unit at an edge node of an operational domain in said communication system; one or more processors arranged to process said label header stack at said edge node to add a new stack entry having a label field comprising a field for linking a stack field with at least one A value delimited by a header stack entry between other stack domains, said one stack domain can be set by a node belonging to said operational domain of said label switching protocol of said communication system, said at least one other stack domain Can be set by a node belonging to another operation domain of the communication system. 12. A method of removing boundary markers in a header stack of a business unit, said header stack conforming to a label switching protocol and comprising a plurality of headers, each of these headers comprising a label field to which a label value can be assigned, to Enabling a label switching node to operate on a packet in a network operation domain of a label switching protocol in a communication system comprising a plurality of networks, the method comprising the steps of: receiving the packet at an edge node of an operational domain of the communication system; processing said label header stack at said edge node to remove stack entries having a label field comprising a boundary for said header stack entry between a stack domain and at least one other stack domain Marking values, said one stack domain can be set by said node belonging to the first operational domain of said label switching protocol of said communication system, said at least one other stack domain can be set by said communication system Nodes of another operational domain to set. 13. A communication system comprising a plurality of Multi-Protocol Label Switching communication networks, each said communication network comprising a plurality of network nodes arranged to implement a Multi-Protocol Label Switching domain of operation, the system comprising: A boundary node located between two said communication networks, the boundary node comprising: a receiver configured to receive MPLS; and one or more processors configured to process the received MPLS header stack of the traffic unit to include a delimited tag field value indicating that the two The operational boundary of the Multiprotocol Label Switching operational domain of a communication network. 14. The system of claim 13, wherein the node is an ingress node to one of the two communication networks, and wherein the node further comprises one or more processors, the The one or more processors are configured to perform the following processes: The header stack is processed to contain one or more other MPLS header field values after assigning the operational boundary label field value such that other A node is capable of performing one or more operations on the business unit.

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